PR Summary

github.com//issues/10789
As seen in the issue link above, a simple way to generate a pie graph is using plt.pie, and the second method to generate a pie graph is by using plt.subplots. Both of these approaches creates the pie graph through _axes.py by using an Axes instance which calls its pie method; the additional line to add calls the set_aspect function, which sets the aspect of the axis scaling, with ‘equals’ as parameters and this results in a default circular pie graph with an equal aspect ratio as wanted.

Here is the travis test: https://travis-ci.org/jerrylui803/matplotlib/builds/358696515

PR Checklist

• Has Pytest style unit tests
• Code is PEP 8 compliant
• New features are documented, with examples if plot related
• Documentation is sphinx and numpydoc compliant
• Added an entry to doc/users/next_whats_new/ if major new feature (follow instructions in README.rst there)
• Documented in doc/api/api_changes.rst if API changed in a backward-incompatible way